# Commission Delegated Regulation (EU) 2015/68 of 15 October 2014 supplementing Regulation (EU) No 167/2013 of the European Parliament and of the Council with regard to vehicle braking requirements for the approval of agricultural and forestry vehicles (Text with EEA relevance), Appendix 4

Extent: E+W+S+N.I.

Method of selection of the low-adhesion surface
1.
Details of the coefficient of adhesion of the surface selected, as determined in point 5.1.1.2 of this Annex, shall be given to the technical service.
1.1.
These data shall include a curve of the coefficient of adhesion versus slip (from 0 % to 100 % slip) for a speed of approximately 40 km/h.
Until a uniform test procedure is established for the determination of the adhesion curve for vehicles with a maximum mass exceeding 3,5 tonnes, the curve established for passenger cars may be used. In this case, for vehicles with a maximum mass exceeding 3.5 tonnes, the ratio kpeak to klock shall be established using a value of kpeak as defined in Appendix 2. With the consent of the technical service, the coefficient of adhesion described in this item may be determined by another method provided that the equivalence of the values of kpeak and klock are demonstrated.
1.1.1.
The maximum value of the curve will represent kpeak and the value at 100 % slip will represent klock.
1.1.2.
The ratio R shall be determined as the quotient of the kpeak and klock.
R = k peak k lock 1.1.3.
The value of R shall be rounded to one decimal place.
1.1.4.
The surface to be used shall have a ratio R between 1,0 and 2,0.
Until such test surfaces become generally available, a ratio R up to 2,5 is acceptable, subject to discussion with the technical service.
2.
Prior to the tests, the technical service shall ensure that the selected surface meets the specified requirements and shall be informed of the test method to determine R, the type of vehicle (tractor, etc.) and the axle load and tyres (different loads and different tyres have to be tested and the results shown to the technical service which will decide if they are representative for the vehicle to be approved).
2.1.
The value of R shall be mentioned in the test report.
The calibration of the surface has to be carried out at least once a year with a representative vehicle to verify the stability of R.

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Source: https://www.legislation.gov.uk/eur/2015/68/annex/XI/appendix/4 (the official version)
Page: https://openlegislation.uk/eu-regulation-2015-68/annex-XI/appendix-4
Contains public sector information licensed under the Open Government Licence v3.0. Source: legislation.gov.uk, The National Archives.